Benchtop testing is required prior to fielding an ad-hoc wireless network. An ad-hoc network often consists of a large number of RF modems making up the nodes of the network. A test setup must be scalable and rapidly configurable to test differing numbers of nodes and ad-hoc scenarios. The topologies must reflect a reasonable subset of all possible ad-hoc topologies while sufficiently stressing the capability of the network in order to obtain a high degree of confidence that the network and modems are working correctly.
Current testing methods typically range from simply setting up the test in an open air environment to connecting the wireless equipment together via cables, to assembling test setups disposed within RF shielded rooms. Although open air test setups have the advantage of being simple to construct, they typically suffer from a variety of problems. First, the open air environment is difficult to control. It is not possible to precisely control signal levels and test topologies in order to verify protocol implementation. Often, due to intermittent interference, specific tests cannot be repeated with consistent results. Second, each test setup takes up at least one radio channel and because radio channels are regulated and allotted by the government they are a scarce resource. Thus, an active test lab may use all of the allotted channels for one test setup thereby preventing multiple independent test setups from operating simultaneously and preventing multiple engineers or production workers from working side by side.
One way to overcome the limitations of the open air test setup is by connecting the test setup to wireless equipment through an RF cable system having RF cables, RF combiners and RF attenuators. Using this approach, transmitter signals can be communicated to the wireless system receivers via the RF cable system. Not only does this allow the signal power levels to be controlled using RF attenuators, but the setup can support flexible network topologies in a controlled environment under repeatable test conditions.
Nevertheless, there still are shortcomings associated with conventional test setups using RF cables, combiners and attenuators. For example, for robust testing path loss with fading channels should be simulated across various node to node routes. Path loss variations should be rapidly switchable to speeds approaching the required fading correlation times. Moreover, the test setup should not allow undesired crosstalk to occur between the modem/nodes. Furthermore, the test setup must be automatable for repeatability and accuracy. Conventional test systems fail to address such combination of shortcomings.
In view of the above, there is a strong need in the art for a test setup for testing broadband wireless modems and networks. More specifically, there is a strong need for a test setup which can simulate path loss with fading channels across various node to node routes. There is a strong need for a test setup which can rapidly switch path loss variations at speeds approaching required fading correlation times. Moreover, there is a strong need for a test setup that avoids undesired crosstalk and that is automatable for repeatability and accuracy.